The submodules of testsuite/integration did not appear while importing WildFly in IntelliJ IDEA as maven project. Solution is the https://www.jetbrains.com/help/idea/maven-importing.html chapter VM options for the importer.
The option in use for the IntelliJ import must be -DallTests causing the testsuite/pom.xml (only integration by default) and testsuite/integration/pom.xml to have modules (none by default now).